Commas, em dashes, periods, and more

Punctuation Best Practices


When listing 3 or more items in a sentence, use the serial/Oxford comma.

  • The permit will be mailed, emailed, or faxed.
  • Participants in this organization include regulatory agencies, consumer groups, food service and retail store trade associations, and retail food facility operators.

Em Dash

Use an em dash (the long dash) to mark a sudden break or abrupt change in thought. Do not use spaces before or after the em dash.

  • TSA Precheck—a new service for regular travelers—can help you get through the airport faster.
  • After days of deliberation, the jury came to its final verdict—not guilty.

En Dash

An en dash (the shorter dash) expresses a range of values (times, years, dollar amounts). Do not use spaces before or after the en dash.

  • The rent could cost between $1,500-2,000 per month.


Use a colon to give emphasis, present dialogue, introduce lists or text, and clarify composition titles.

  • They studied hard for one purpose: to succeed in their college courses.


Semicolons link two independent clauses that are closely related in thought and not joined by a conjunction (e.g., and, but, if), such as when restating the preceding idea with a different expression.

  • The Steelers had too many fumbles; they lost the game.
  • I ordered a salad; I didn’t have enough time to prepare lunch this morning.


While the ampersand symbol can reduce the length of copy and give the eye a break when scanning content, the Commonwealth does not replace the “and” with “&” in its copy. However, if a brand uses the ampersand in its name, the ampersand should be used when referencing the brand by name.

  • Simon & Schuster

Signs and symbols

Use abbreviations, acronyms, and symbols to save space, improve readability and scanning, and to avoid distracting the reader with repeated use of words or phrases.

  • Degree Mark ° The degree mark is used instead of the word “degree”, following a figure denoting measurement.
  • Percent Symbol % Always use the percent symbol, rather than spelling out the word, when referencing percentages, because it improves the content’s scannability.
  • Letter Symbols These are typically used in measurement (e.g., cm2) and mathematical equations (π). While they’re uncommon for a government website, they’re included in the appendix for your reference.

Numbers and numerals

Use the following guidelines when using numbers, including referencing monetary amounts:

  • Present all numbers as numerals; this applies to ordinal numbers as well (e.g., 1st, 3rd, 95th)
  • Spell out the number as a word if it starts a sentence or follows an em dash
  • Telephone numbers are formatted XXX-XXX-XXXX with no leading nation code. Vanity telephone numbers, such as 1-800-986-KIDS should be immediately followed by the numeric equivalent in parentheses (1-800-986-5437)
  • When referencing numbers below 999,999 use numbers.
  • When referencing numbers above 999,999 use words (e.g., million, billion, trillion) or a combination of words and numbers (e.g., 1.6 million).
  • Avoid stating a monetary amount at the beginning of a sentence.


  • Time refers to time of day.
  • Use the 12-hour clock
    •  Example: 7:30 p.m.
  • Separate hours and minutes with a colon
    • Example: 10:45 a.m.
  • Do not use minutes with on-the-hour times
    • Example: 2 p.m.


Daypart refers to a.m. and p.m.

  • Write daypart in lowercase with periods after each letter
    • Example: 7:30 p.m.
  • Separate time and daypart with a single space
    • Example: 10:45 a.m.
  • Use en dash without spaces to indicate from/to in time ranges
    • Example: 8 a.m.–6 p.m.

Time zones

Time zones refer to US time zones.

  • Standard/daylight saving time indicator for time zones should be excluded
    • Example: ET, and not EST or EDT
  • Base time zone for copy should be Eastern Time (ET) with no requirement to translate for other time zones


Days refer to days of the week.

Abbreviate days of the week:

  • Mon.
  • Tue.
  • Wed. 
  • Thur.
  • Fri.
  • Sat.
  • Sun.

Use a period at the end

Use en dash without spaces to indicate from/to in day ranges

  • Example: Mon.–Fri.

Avoid using Exclamation Points

Exclamation Points are generally used for emphasis. However, they can be easily overused, misused, and can come across as aggressive.

Try using a period instead. You’ll see it works as well, if not better.